Two main approaches to the stabilization of edible oils containing high linolenic acid levels involve the addition of antioxidants or hydrogenation of the oils. An antioxidant, as the name implies, tends to prevent oxidation. Natural antioxidants present in foods include lecithin, vitamin E, and certain sulfur-containing amino acids. However, the most effective antioxidants are synthetic chemicals approved by the Food and Drug Administration for addition to foods. Without these antioxidants, food products such as crackers, potato chips, breakfast cereals, fat-containing dehydrated foods, and many other fatty foods could not be stored as long without developing off-flavors and rancidity. As mentioned above, this is particularly true of crackers and other snack items to which oil is often applied while they are warm so that the oil penetrates the product somewhat and improves bite and mouthfeel while a portion remains on the surface to provide a desirable sheen.
Among the common antioxidants are butylated hydroxyanisole (BHT), butylated hydroxytoluene (BHT), tertiary butylated hydroquinone (TBQH), and propyl gallate. Other diverse materials such as ascorbic acid, stannous chloride, and tocopherols (vitamin E) can perform the function of antioxidants. Some food additives serve dual roles; sulfur dioxide, for example, can function both as a preservative and an antioxidant. Many consumers eschew oils containing synthetic antioxidants, however, due to studies suggesting they might have mutagenic and carcinogenic properties.
In addition to synthetic antioxidants, hydrogenation is also used to stabilize oils against oxidation. Hydrogenated coconut oil is a preferred spray oil, but partially hydrogenated peanut oil and soybean oil are often used as well (Bailey's Industrial Oil and Fat Products, 4th ed., vol. 3, John Wiley, New York, 1985, page 109). However, hydrogenation produces substantial amounts of trans fatty acids not present in natural oils, which contain only cis double bonds, particularly where the oils are partially hydrogenated. Trans fatty acids have been recently shown to raise low density lipoprotein cholesterol levels and to lower high density lipoprotein serum cholesterol levels in adults fed fats having these acids (Mensink, R. P., and Katan, M. B., New Eng. Jour. Med. 323: 439-445 (1990)). Hence, many consumers suspect that food products containing hydrogenated or partially hydrogenated oils may be unhealthy.
It would be desirable to have a natural antioxidant for edible oils, particularly for oils especially susceptible to oxidation such as high linolenic oils, e.g., soybean oil and canola (which has the lowest concentration of saturated fatty acids of commercial edible oils), that are used as spray oils on food products.